In the field of graphic arts, in order to optimize the reproduction of a continuous tone image or line image from a halftone image, an image formation system which exhibits an ultrahigh contrast (particularly gamma of 10 or more) is required.
As a process for the formation of a high contrast image there can be used a lithographic development process employing a so-called "infectious development effect". However, this lithographic development process is disadvantageous in that the developer is too instable to be used.
As a solution to the foregoing problem, an approach has been proposed which comprises the use of a stabler developer as described in U.S. Pat. Nos. 4,224,401, 4,168,977, 4,166,742, 4,311,781, 4,272,606, 4,221,857, 4,332,878, 4,634,661, 4,618,574, 4,269,922, 5,650,746, and 4,681,836.
In this image formation system, a surface latent image type silver halide photographic material comprising a hydrazine derivative incorporated therein is developed with a stable MQ developer (developer comprising hydroquinone and p-aminophenol in combination) or PQ developer (comprising hydroquinone and 1-phenyl-3-pyrazolidone in combination) having a pH value of from 11 to 12.3 to obtain an ultrahigh negative image having .gamma. of more than 10. In accordance with this process, an ultrahigh contrast and a high photographic sensitivity can be obtained. Further, a high concentration sulfite can be added to the developer. Accordingly, the developer thus obtained exhibits a remarkably improved stability to air oxidation as compared with the conventional lith developers.
With respect to bright room light type photographic light-sensitive materials for contact work for use in plate collection and reflecting steps, too, in order to effect faithful superposition and reflection of halftone original and line image original, a process for the formation of an ultrahigh contrast image is required. To this end, the foregoing image formation system employing a hydrazine derivative can be effectively employed. Specific examples of the application of this system are disclosed in JP-A-62-640 (The term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-A-62-235938, JP-A-235939, JP-A-63-104046, JP-A-63-103235, JP-A-63-296031, JP-A-63-314541, and JP-A-64-13545.
On the other hand, it is well known that endiols such as ascorbic acid act as a developing agent. Endiols have been noted as an ecologically or toxicologically harmless developing agent. For example, U.S. Pat. Nos. 2,688,549 and 3,826,654 propose that an image can be formed under an alkaline condition having a pH range of not lower than 12. However, these image formation processes cannot provide a high contrast image.
Some attempts have been made to raise contrast in a development system employing ascorbic acid. For example, Zwicky proposes that a lithographic effect is exerted when ascorbic acid is used as the sole developing agent (J. Photo. Sc., Vol. 27, page 185 (1979)). However, this development system provides a remarkably low contrast as compared with the hydroquinone development system. Further, U.S. Pat. No. T 896,022 and JP-B-49-46939 (The term "JP-B" as used herein means an "examined Japanese patent publication") disclose a development system employing bis quaternary ammonium salt and ascorbic acid. However, this development system shows some development accelerating effect but little or no effect of raising contrast. JP-A-3-249756 and JP-A-4-32838 disclose an effect exerted by the combined use of ascorbic acid and quaternary salt. However, the image thus obtained has an insufficient contrast. JP-A-5-88306 proposes that a high contrast can be obtained by keeping the pH value to not less than 12.0 with ascorbic acid as the sole developing agent. However, this development system is disadvantageous in that the developer used has a poor stability.
There is a case where the use of a special developer comprising as main components ascorbic acid and a hydrazine derivative can provide a development system that can give a high sensitivity and minimized generation of stain and fog (U.S. Pat. No. 3,730,727). However, no reference is made to the enhancement of contrast.
JP-A-7-13306 discloses a method which comprises the development of a photographic light-sensitive material comprising a hydrazine compound with a developer containing ascorbic acid. However, this method is disadvantageous in that the developer use has a pH value of not less than 10 and thus leaves something to be desired in stability. Further, when the pH value of the developer is not more than 10, a sufficient hardness in contrast cannot be obtained.
It is well known that a quaternary onium salt compound is incorporated in a photographic light-sensitive material. Such a photographic material is disclosed in JP-A-6-43602, JP-A-6-102633, JP-A-6-161009, and JP-A-5-142687. However, all these photographic light-sensitive materials proposed exhibit a pH value of not less than 10. These photographic light-sensitive materials are apt to air oxidation and variation of properties due to fatigue of the developer with time.
JP-A-5-53231 discloses that a photographic light-sensitive material comprising a special silver halide emulsion and a quaternary onium salt compound is processed in a pH range of not more than 10 to provide a hard contrast. However, when such a silver halide emulsion is used, development proceeds slowly, making it impossible to obtain practically sufficient properties. JP-A-5-273708 discloses that a photographic light-sensitive material comprising a quaternary onium salt compound is processed with a developer containing ascorbic acid (pH 9.6) to provide a hard contrast. However, sine this development system requires the use of a quaternary onium salt in a large amount, development proceeds slowly and reduced Dmax is given, making it impossible to obtain practically sufficient properties.
JP-A-62-250439 and JP-A-62-280733 disclose that a photographic light-sensitive material comprising a hydrazine derivative and a quaternary onium salt compound is processed with a developer having a pH value of not less than 11 to form a hard contrast image. Further, JP-A-61-47945, JP-A-61-47924, JP-A-1-179930, and JP-A-2-2542 disclose that a photographic light-sensitive material comprising an emulsion having a silver bromide content of 50 mol %, a specific hydrazine derivative and a quaternary onium salt compound is developed with a developer having a pH value of not less than 11 to form a hard contrast image. However, since all these development systems employ a developer having a pH value of not less than 11, the photographic light-sensitive material is apt to air oxidation and variation of properties due to fatigue of the developer with time.
The process for the formation of a hard contrast image using a hydrazine derivative is well known and has found wide application to photomechanical process. However, this development system normally requires the use of a developer having a high pH value which is apt to air oxidation and thus is instable.
Attempts have been made to develop a silver halide photographic material comprising a hydrazine compound with a developer having a lower pH value to form a hard contrast image.
JP-A-1-179939 and JP-A-1-179940 disclose a processing method which comprises the development of a photographic light-sensitive material comprising a nucleation and development accelerator containing an adsorption group for silver halide emulsion grains and a nucleating agent containing similar adsorption group with a developer having a pH value of not more than 11.0.
U.S. Pat. Nos. 4,998,604 and 4,994,365 disclose a hydrazine compound having a repeating unit of ethylene oxide and a hydrazine compound having a pyridinium group. However, as shown in examples of these patents, these hydrazine compounds cannot provide a sufficient contrast, and it is difficult to provide a hard contrast and a necessary Dmax under practical development conditions.
Further, the pH value of a developer rises as the concentration of the developer rises due to air oxidation or evaporation of water or drops as the developer absorbs CO.sub.2 gas in the air or is used to develop a photographic light-sensitive material. Thus, the pH value of the developer cannot be kept constant. As the pH value of the developer varies, variation occurs in photographic properties, particularly contrast. Thus, the developer must be replenished at a high rate.
Thus, an image formation process has been desired which can employ a developer having a lower pH value and is insusceptible to variation of photographic properties with pH variation. However, the prior art image formation technique leaves something to be desired.
On the other hand, attempts have been made to substitute ascorbic acid for hydroquinone, which has heretofore been commonly used, for the purpose of lessening the adverse effect on environment. JP-A-6-505574 (corresponding to WO 93/11456), and U.S. Pat. Nos. 5,236,816 and 5,264,323 disclose an image formation process which comprises the processing of a silver halide photographic material comprising a hydrazine derivative with a developer containing ascorbic acid. In this description, a hard contrast image cannot be obtained unless a 3-pyrazolidone derivative is used as an ultraforming auxiliary developing agent in combination with an ascorbic acid developing agent and the developer used has a relatively high pH value to obtain a hard contrast image. In fact, as a result of the inventors' supplementary examination, an ultrahigh contrast cannot be obtained unless the pH value of the developer is as high as not less than 11.0. Further, this development system has a great disadvantage that when air-oxidized or fatigued from processing of film, the developer shows a remarkable pH drop that extremely impairs contrast.
EP 573,700 discloses a development process which comprises the replenishment of a developer comprising ascorbic acid and a 3-pyrazolidone derivative in combination with a replenisher having substantially the same composition as the developer but a higher pH value than the developer. However, the above cited European Patent has no reference to an ultrahigh contrast photographic light-sensitive material comprising a hydrazine derivative. As previously mentioned, when the developer comprising ascorbic acid and a 3-pyrazolidone derivative in combination exhibits a pH value of from 9.0 to 10.5, the ultrahigh contrast photographic light-sensitive material comprising a hydrazine compound cannot provide an ultrahigh contrast. When the developer has an alkalinity as high as not less than pH 11.0, an ultrahigh contrast can be obtained. However, the developer shows a remarkable pH drop due to air oxidation. When the replenisher having a high pH value is used, this tendency becomes more remarkable, making it almost impossible to keep the pH value of the developer constant during running processing.
As mentioned above, the ultrahigh image formation system using a hydrazine derivative employs a dihydroxybenzene compound such as hydroquinone as a developing agent and thus is somewhat disadvantageous from the ecological and toxicological standpoints of view. For example, hydroquinone exerts an allergenic effect and thus is an undesirable component. 1-Phenyl-3-pyrazolidones are components having a poor biodegradability. Further, a high concentration sulfite shows a high COD (chemical oxygen demand) value. Moreover, this image formation system normally employs amines described in U.S. Pat. No. 4,975,354 as well. However, these amines are undesirable from the standpoint of toxicity and volatility.